Navigation systems are now widely used in vehicles in which they can be fixedly or removably installed. Navigation systems assist a driver in route planning and provide directions as well as information on portions of a road network. In order to provide a graphical representation, a database including geographic map data is accessed and a map viewer generates a map view which helps the driver to follow a calculated route.
Information displayed on the navigation system may be easily modified and adapted, e.g. by changing the zoom level of the displayed map portion, by displaying additional objects that might be of relevance to the user or by highlighting objects that may be of relevance to the user. In particular, 3-dimensional map views became popular, as they are of particular value to the user owing to their high recognition quality. Various map objects, such as buildings or other landmarks can be included in 3-dimensional map views or city models output to the user. Depending on the position of the user of the navigation system and the viewing direction, the navigation system calculates the 3-dimensional map view in real time. The computational effort to calculate this 3-dimensional map view in real time for output to the user is time-consuming and the calculation effort can be high in dependence on the number of objects to be displayed.